In access link and node redundancy for service provider based Layer 2 Virtual Private Network (L2VPN) services, customers typically desire resilient site multi-homing access capabilities that are similar to Layer 3 VPN services. However, redundancy in the L2VPN topologies are much more complex compared to Layer 3 VPN topologies because of potential Ethernet frame looping conditions.
One solution to avoid looping conditions is to apply a spanning tree protocol. However, the spanning tree protocol has problems with scalability, and can also result in looping conditions if the spanning tree protocol is misconfigured. Additionally, the spanning tree protocol is typically run “over the top” of a service provider's network and thus the service provider has no control or visibility that the solution is enabled and working properly. Another solution to avoid looping conditions, which the service provider can control, is to use Multi-Protocol Border Gateway Protocol (MP-BGP) with virtual endpoint identifiers (VE-ID). Typically, each provider edge router would have just one VE-ID, and as a result, the VE-ID is used to uniquely identify each provider edge router to the rest of the network. However with a multi-homing approach, the same VE-IDs need to be shared across multiple provider edge routers, thus each VE-ID no longer uniquely identifies each provider edge router. Rather, each VE-ID is reassigned to identify uniquely each multi-homed device (e.g., a customer edge router). Therefore, the original intent and benefits of the VE-ID is lost and it becomes an attribute of the multi-homed device rather than the provider edge router, which is not a scalable solution. That is, with the VE-IDs being attributes of multi-homed devices, more information and data are signaled within the context of a service, and such signaling can be inefficient and complicated to implement and can result in scalability issues in signaling.